OpenCL中不允许使用可变长度数组声明-为什么? [英] variable length array declaration not allowed in OpenCL - why?

问题描述

我想在我的OpenCL内核中创建一个本地数组，其大小取决于内核的参数.看来这是不允许的-至少在AMD APP中是这样.

I want to create a local array inside my OpenCL kernel, whose size depends on a parameter of the kernel. It seems that's not allowed - at least with AMD APP.

您的经历与众不同吗?也许只是APP?还是这里有一些理由?

Is your experience different? Perhaps it's just the APP? Or is is there some rationale here?

现在，我建议在CPU端代码中也应允许使用可变长度数组，这是C标准委员会的不幸选择；但问题仍然存在.

I would now suggest variable length arrays should be allowed in CPU-side code too, and it was an unfortunate call by the C standard committee; but the question stands.

推荐答案

您可以动态分配本地块的大小.您需要将其作为内核的参数，并在调用clSetKernelArg时定义其大小.

You can dynamically allocate the size of a local block. You need to take it as a parameter to your kernel, and define its size when you call clSetKernelArg.

定义示例:

__kernel void kernelName(__local float* myLocalFloats, ...)

主机代码:

clSetKernelArg(kernel, 0, myLocalFloatCount * sizeof(float), NULL); // <-- set the size to the correct number of bytes to allocate, but use NULL for the data.

在执行此操作之前，请确保您知道设备上的本地内存限制是多少.调用clGetDeviceInfo，然后轮询"CL_DEVICE_LOCAL_MEM_SIZE"值.

Make sure you know what the limit for local memory is on your device before you do this. Call clGetDeviceInfo, and poll for the 'CL_DEVICE_LOCAL_MEM_SIZE' value.

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